Effective diabetes self-management is key to maintaining euglycemia and reducing the morbidities associated with type 1 diabetes mellitus (T1D). Adherence to the complex regimen required to achieve ideal hemoglobin A1C (HbA1C) is commonly sub-optimal in adolescents with T1D. Thus, there is a critical need for a diabetes self-management intervention approach that integrates the key elements of proven strategies in a way that is of practical relevance to clinical management and immediately applicable, and that is tailored to address barriers to adherence for individual youth living with T1D. Our specific objective is to complete the study group administrative tasks required to begin enrolling patients in the Flexible Lifestyles (FL3X) RCT. The FL3X intervention, developed and piloted by our team (R21 DK085483, Mayer-Davis and Seid), uses MI to facilitate problem-solving skills training to achieve specific behavioral targets. Specifically, FL3X will employ the methods of adaptive interventions in which patient response to a first-line treatment (FL3X Basic) determines subsequent assignment to a second-line treatment (FL3X Support for responders or FL3X Enhance for non- responders). FL3X Enhance uses additional modular components or 'toolboxes' to further tailor the FL3X intervention to a patient's barriers to adherence related to family communication, diabetes education, social support and diet and physical activity adherence. Our recently completed multisite pilot of FL3X Basic included 61 youth with T1D age 13-16 yrs, randomized to 31 intervention, 30 control (overall 53% at-risk due to low income, minority race/ethnicity, or single parent household) and demonstrated feasibility, acceptability, and promising effects. Attendance at 3 required intervention sessions over a 3-month period was excellent (>90% attendance at each) and 58 of 61 (95%) attended the end-of-study measurement visit. Intervention acceptability was high: 100% of intervention youth said they would recommend FL3X to others. HbA1c decreased by > 0.5% among 41% of intervention participants, compared to 24% of control participants. As for our pilot work, the fully powered FL3X RCT will be coordinated from the University of North Carolina at Chapel Hill, and will include 200 youth, randomized within each of 2 sites that participated in the FL3X Pilot (University of Colorado Denver, Barbara Davis Center for Childhood Diabetes (n=120); and Cincinnati Children's Hospital Medical Center, Division of Pediatric Endocrinology (n=80)). Aims for this Planning Grant are: Aim 1: To refine and supplement the existing FL3X materials required for submission to the Institutional Review Boards at each participating site, Aim 2: To update the existing FL3X website, including both study staff and participant interfaces, and including an update of the underlying data management system Our team has the collaborative history and experience to mount a fully powered RCT of FL3X with high fidelity. Upon completion of work in Planning Grant, we will be ready for immediate implementation of the FL3X RCT. PUBLIC HEALTH RELEVANCE: The FL3X adaptive intervention is an innovative behavioral approach to address the compelling health risks and unique daily life challenges to optimal diabetes self-management experienced by youth with T1D. If proven effective, FL3X will have immediate clinical applicability to improve metabolic status and quality of life for youth with T1D